5-Hydroxytryptamine cardiovascular effects

Navari RM, Koeller JM. Comment electrocardiographic and cardiovascular effects of the 5-hydroxytryptamine-3 receptor antagonists. Authors reply. Arm Pharmaco r (2003) 37, 1918-19. 

Serotonin (4.109, 5-hydroxytryptamine, 5-HT) is a central neurotransmitter that is also found peripherally in the intestinal mucosa and in blood platelets, where its role is incompletely elucidated it even occurs in plants such as bananas. Although there is an enormous literature on the biochemistry and pharmacology of serotonin, our knowledge of its biological role remains somewhat fragmented. The diverse physiological effects of 5-HT influence the cardiovascular system, the cerebrovascular system, the digestive... 

Serotonin (5-hydroxytryptamine [5-HT]) produces its effects through a variety of membrane-bound receptors, located in the central and peripheral nervous systems and in non-neuronal tissues in the gastrointestinal tract, cardiovascular system, and blood. The knowledge of the anatomical localization of the receptors is an important step forward for the understanding of their function. Several techniques allow the microscopic visualization of the sites of expression of these receptors in the tissues. In this review, we will attempt to summarize the available information on the neuroanatomical organization of each one of the 5-HT receptor subtypes. 

Serotonin (5-hydroxytryptamine, 5-HT) is synthesised in enterochromaffin cells, largely in the gut, and also extensively taken up into blood platelets from which it is released to have vascular effects. It has complex effects on the cardiovascular system, varying with the vascular bed and its physiological state it generally constricts arterioles and veins and induces blood platelet aggregation it stimulates intestinal and bronchial smooth muscle. Carcinoid tumours secrete serotonin and symptoms may be benefited by serotonin antagonists, e.g. cyproheptadine, methysergide and sometimes by octreotide (see Index). It is a neurotransmitter in the brain. 

Further evidence that central 5-hydroxytryptamine (5-HT) neurones are involved in cardiovascular control systems is found in the observation that a central administration of the selective neurotoxin 5 6-dihydroxy-tryptamine causes a significant delay in the development of hypertension in young spontaneously hypertensive rats (SHRs).30 a further demonstration of the centrally-mediated hypotensive effect of methysergide has appeared 31 this may not be a result of 5-HT antagonism. 

---